#include<iostream>
#include<string>
#include <vector>
#include<unordered_map>
using namespace std;


//#include"Hashtable.h"
//#include"unoderedMap.h"
//#include"unoderedSet.h"
//#include"BitSet.h"
//#include"BloomFilter.h"
//int main()
//{
//	//jt::test_unordered_set();
//	//jt::test_unordered_map();
//	//test_twobitset();
//	TestBloomFilter();
//}


	bool containsDuplicate(vector<int>& nums) {
		unordered_map<int, int>hash;
		for (int i = 0; i<nums.size(); i++)
		{
			hash[nums[i]]++;
		}

		for (auto& e : hash)
		{
			if (e.second >= 2)return true;
			else return false;
		}
	
	}


int main()
{
	vector<int>nums = { 1, 2, 3, 1 };
	cout << containsDuplicate(nums) << endl;
}